1. Field of the Invention
The present invention relates to graphics and drawing applications for computers, and more particularly to a method for the interactional presentation of graphics through a coupled network of intelligent computer work stations.
2. Brief Description of the Prior Art
Many presentation graphics and drawing applications exist for computers. Some notable examples are MacDraw for Apple Macintosh computers and SunDraw for Sun Microsystems work stations. These programs allow the user to prepare graphical drawings depicting virtually any subject matter. However, they are limited in that they allow only one person to work on the drawing at a time; they do not allow interactive networking of the graphical drawings.
Methods and computer programs do exist which allow users to share information over a network simultaneously, but these are not graphically oriented. The most notable example of this is a program called TALK, which is available as part of 4.3 BSD UNIX. This program allows one user using a work station to initiate a conversation with another user on a different work station. The program allows only the transfer of textual information. Once a conversation is started, the program splits the screen horizontally. The characters inputted by user A appear on the top half of A's screen, and simultaneously appear on the lower half of the screen on the user B's work station. In like manner, when user B types on B's work station, the input appears on the top half of B's screen and the bottom half of user A's screen. In addition to the fact that the TALK program only allows sharing of textual information, it is limited in that the conversation can be between only two users.
There is also a freely available public domain program for the X-Windows system called WScrawl which allows users to share graphical information. However, it works by taking advantage of special features of X-Windows. A simple program is run which opens a single window on each of multiple machines. Then graphics drawn in one window is replicated in the other windows by making identical X-Windows protocol requests. This differs from the current invention in several ways. First, there is only one program being run. Second, the graphics being drawn is not reduced to its essence and then transmitted. Rather, the graphics are merely drawn in multiple windows which are located on different machines. This approach has any disadvantages. First of all, there is no way to distinguish between what multiple users have drawn; everything is merged together. Second, since the essence of the graphic is not transmitted, there is no way for another user to "grab" the image and modify it. Third, and possibly most importantly, this scheme will work only under the X-Windows system. There is no way to make it interoperate with other windowing systems such as Apple's MacOS or Microsoft's MSWindows. The current invention has none of these restrictions.
Finally, the PostScript page description language has been used to transmit graphical information over a network, most notably in Sun Microsystems NeWS (Network Extensible Windowing System). However, PostScript has no facilities for describing the interactions which a user might engage in when using a drawing program. For example, PostScript has no means of indicating that a specific object has moved from one location to another, or that an object has been cut. In fact, the notion of a graphical object is alien to PostScript, which is suited mainly to describing static images so they can be printed.